Electrical stimulation can be useful for treating a variety of conditions. Deep brain stimulation can be useful for treating, for example, Parkinson's disease, dystonia, essential tremor, chronic pain, Huntington's disease, levodopa-induced dyskinesias and rigidity, bradykinesia, epilepsy and seizures, eating disorders, and mood disorders. Typically, a lead with a stimulating electrode at or near a tip of the lead provides the stimulation to target neurons in the brain. Magnetic resonance imaging (“MRI”) or computerized tomography (“CT”) scans can provide a starting point for determining where the stimulating electrode should be positioned to provide the desired stimulus to the target neurons.
After the lead is implanted into a patient's brain, electrical stimulus current can be delivered through selected electrodes on the lead to stimulate target neurons in the brain. Typically, the electrodes are formed into rings disposed on a distal portion of the lead. The stimulus current projects from the ring electrodes equally in every direction. Because of the ring shape of these electrodes, the stimulus current cannot be directed to one or more specific positions around the ring electrode (e.g., on one or more sides, or points, around the lead). Consequently, undirected stimulation may result in unwanted stimulation of neighboring neural tissue, potentially resulting in undesired side effects.
In one embodiment, a stimulation lead includes a lead body having a longitudinal surface, a distal end portion, a proximal end portion, and a longitudinal length. Terminals are disposed along the proximal end portion of the lead body. Electrodes are disposed along the distal end portion of the lead body. Conductors electrically couple the terminals to the electrodes. The electrodes include segmented electrodes. Each of the segmented electrodes includes a proximal end, a distal end, an exterior surface, an interior surface opposite the exterior surface, a first side-wall extending radially between the interior surface and the exterior surface from the distal end to the proximal end, and a second side-wall opposite to the first side-wall and extending radially between inferior surface and the exterior surface from the distal end to the proximal end. At least one of the segmented electrodes defines at least one open cavity formed along the first side-wall of the segmented electrode and extending circumferentially inwardly and extending from the distal end to the proximal end. The at least one open cavity is configured and arranged to facilitate adhesion of the segmented electrode to the lead body.
In another embodiment, a method of making a stimulation lead includes disposing at least one pre-electrode along a distal end portion of a lead body. The at least one pre-electrode includes a substantially-cylindrical body having an outer surface, an interior surface opposite the outer surface, a proximal end, and a distal end. The body includes a plurality of segmented electrodes disposed along the body in a spaced-apart configuration. Each of the plurality of segmented electrodes extends between the proximal end and the distal end of the body. Each of the plurality of segmented electrodes also extends between the interior surface of the body and an exterior surface. Each of the plurality of segmented electrodes includes a first side-wall and a second side-wall opposite to the first side-wall. The first side-wall and the second side-wall each extend radially between the interior surface and the exterior surface from the distal end to the proximal end. The plurality of segmented electrodes includes a first segmented electrode and a second segmented electrode. The first segmented electrode defines a first open cavity extending circumferentially inwardly into the first side-wall from the distal end to the proximal end. Connecting material couples the first segmented electrode to the second segmented electrode. A cutout is defined along the body between the first segmented electrode and the second electrode. Non-conductive material is placed within the first open cavity to facilitate retention of the segmented electrode with the lead body.
In yet another embodiment, a pre-electrode for a stimulation lead includes a substantially-cylindrical body having an outer surface, an interior surface opposite the outer surface, a proximal end, and a distal end. A plurality of segmented electrodes is disposed along the body in a spaced-apart configuration. Each of the plurality of segmented electrodes has opposing side-walls extending radially between the proximal end and the distal end of the body. At least one open cavity is defined along at least one side-wall of at least one of the plurality of segmented electrodes. The at least one cavity extends between the proximal end and the distal end of the body. Connecting material is disposed along the outer surface of the body. The connecting material couples each of the plurality of segmented electrodes to one another. A plurality of cutouts is defined between adjacent segmented electrodes of the plurality of segmented electrodes. At least one alignment feature forms an opening extending between the outer surface of the body and one of the plurality of cutouts.